Viability of Trichomonas vaginalis in Copan Universal Transport Medium and ESwab™ Transport Medium
The prevalence of trichomoniasis, a very common sexually transmitted disease (STD) caused by the parasitic protozoan Trichomonas vaginalis, has been estimated from National Health and Nutrition Examination Survey data to be approximately 3.1% in the United States among women of reproductive age and as high as 13.3% in African Americans (4). Furthermore, trichomoniasis is a risk factor for preterm birth and a marker of high-risk sexual behavior and is often associated with other reportable STDs (2, 5). T. vaginalis is most frequently identified by microscopic examination of vaginal fluid, but this method has a sensitivity of only about 60% compared to that of culture (3). Most physicians’ offices do not maintain media for the culture of T. vaginalis or have the equipment, such as incubators, required for T. vaginalis culture. The goal of this study was to evaluate routine transport media (universal transport medium [UTM®] and ESwab™ transport medium; Copan Diagnostics, Inc., Murrieta, CA) used by many clinics for transport to a formal laboratory setting where delayed culture for T. vaginalis can be performed.
The patients selected for the study met the following criteria: females presenting to the Jefferson County Department of Public Health (Alabama) STD clinic for examination/treatment, post-pubescent and ≥16 years of age, not pregnant, and not having taken metronidazole or tinidazole within 2 weeks of recruitment.
Vaginal swab specimens for T. vaginalis culture were randomized into two equal groups: those stored at room temperature (RT) and those stored at 37°C. All participants, as per the standard of care, were inoculated in the clinic via vaginal swab with an InPouch (Biomed Diagnostics, White City, OR) for T. vaginalis culture; these “bedside inoculated” cultures were kept at 37°C in the clinic and the laboratory and are the gold standard samples for the study. Specimens for transport in UTM® and ESwab™ medium were taken from all participants by using a flocked swab provided with each kit. The UTM® and ESwab™ media inoculated with the RT specimens were stored at RT in the clinic and during transport, and the UTM® and ESwab™ media inoculated with the 37°C specimens were stored at 37°C in the clinic and during transport. In the laboratory, all the UTM® and ESwab™ media were used to inoculate InPouches, which were subsequently incubated at 37°C. Clinic-derived In-Pouches and InPouches inoculated from UTM® and ESwab™ transport medium were evaluated for positive culture for 5 consecutive days. Cultures that failed to grow after 5 consecutive days were recorded as negative for T. vaginalis.
Data were not assumed to be parametric. Alpha values were set at 5%. Sensitivity and specificity results were generated by using the tools provided by the OpenEpi website (Open Source Epidemiologic Statistics for Public Health, version 2.2; A. G. Dean, K. M. Sullivan, and M. M. Soe [http://www.openepi.com /]). All P values are two-tailed. Unless otherwise noted, mid-P values and Fisher’s exact P values are reported. Taylor or conditional maximum likelihood estimates of the odds (OR) are presented with appropriate 95% confidence intervals (CI). The effect of temperature was evaluated by using contingency table analysis. The distributions of age among the participants and the amounts of time the UTM® and ESwab™ media were stored at the specified temperatures before being inoculated by InPouch were evaluated by the Wilcoxon/Kruskal-Wallis rank test (JMP software, version 7.0.1; SAS Institute, Cary, NC).
The total number of individuals screened and accepted into the study was 103. Specimens from one hundred of the women were used for analysis. Specimens from the remaining three women were dropped from the study due to storage errors or inadequate paperwork. Seven percent of the women identified themselves as Caucasian and 89% as African American, and 4% refused to record an answer.
The median amount of time that elapsed between the collection and culture of UTM® and ESwab™ media specimens was 5 h (interquartile range, 21 h) compared to immediate culture with bedside inoculation; four collection times were outliers and were excluded from this subanalysis (hours 70, 71, 72, 72).
We performed several analyses to check the uniformity of the data between the RT and 37°C groups. The distributions of elapsed time between collection and culture was not observed to be significantly different between the RT and 37°C groups (P = 0.734). The median age of the participants was 24 years (interquartile range, 7 years). The age distributions did not significantly differ between the RT and 37°C groups (P = 0.750). Furthermore, the age distributions between culture result (positive/negative) and temperature (RT/37°C) were not significantly different for UTM® (P = 0.530) and ESwab™ medium (P = 0.448).